Centrifugal impact rock crushers of the prior art typically have a vertical drive shaft and a horizontal and impeller table on which are mounted several impeller shoes for throwing the material to be crushed off of the table against peripheral anvils where it is crushed upon impact. Since the impeller components are themselves massive and in addition carry a large load of heavy rock, the drive shaft must be journaled in bearings which are continuously lubricated in order to provide a long-lived crusher. These bearings normally are mounted in a pedestal which surrounds the drive shaft and which provides a reservoir for the oil that is circulated through the bearings.
While oil seals are provided at the top and bottom of the pedestal, to seal the drive shaft against leakage of oil and to prevent foreign matter from contaminating the oil, the top oil seal in particular is quite susceptible to wear and damage. The internal environment of crushers of this type includes large amounts of ground rock and rock dust which is very abrasive and yet is small enough so that it is difficult too mechanically screen from the operative portions of the crusher. Therefore, as the ground rock accumulates around and on top of the pedestal it tends to invade the upper oil seal thereby causing excessive wear and premature seal failure. Because of this condition, the oil seal must be constantly monitored for wear and it must be frequently replaced to prevent the rock from damaging the bearings when the oil seal does fail. As a result considerable labor expense and down time are expended to prevent this occurance. In addition, due to the high abrasiveness of the rock and the quanity of it which builds up adjacent to the seal, often the seal fails unexpectedly, thereby causing bearing failure even though extensive preventive action is undertaken.